EP0730493A1

EP0730493A1 - Use of a polymer material based on modified hydrocolloids as encapsulating material

Info

Publication number: EP0730493A1
Application number: EP95922491A
Authority: EP
Inventors: Rudolf Hinterwaldner; Bruno Hertrich; Wilfried Babel
Original assignee: Omnitechnik Mikroverkapselungs GmbH
Current assignee: Omnitechnik Mikroverkapselungs GmbH
Priority date: 1994-06-06
Filing date: 1995-06-02
Publication date: 1996-09-11
Anticipated expiration: 2015-06-02
Also published as: ATE195890T1; CA2162280C; ES2151961T3; DE4419724A1; WO1995033554A1; US5690869A; EP0730493B1; JPH09501734A; TW284777B; PT730493E; KR960703667A; DE59508683D1; JP3503138B2; DK0730493T3; CA2162280A1; US5690869C1

Abstract

PCT No. PCT/EP95/02107 Sec. 371 Date Oct. 5, 1995 Sec. 102(e) Date Oct. 5, 1995 PCT Filed Jun. 2, 1995 PCT Pub. No. WO95/33554 PCT Pub. Date Dec. 14, 1995The present invention relates to the use of a polymer material based on modified hydrocolloids as covering material for critical working substances.

Description

Use of a polymer material based on modified hydrocolloids as the covering material

The invention relates to the use of a polymer material based on modified hydrocolloids as the covering material.

The commercial economy, industry and handicrafts and do-it-yourself have been looking for and demanding packaging systems for critical working materials for a long time, with which they can be temporarily and / or latently rendered inert for storage, handling and the like. Critical working materials include understood dangerous, flammable, volatile, autoxidable, reactive, thermosensitive, polymerizable and / or toxic compounds which e.g. react prematurely with one another, contaminate the environment and / or harm humans and animals. There are a number of legal requirements for handling critical materials, provided that they include: fall under the regulations on hazardous substances, dangerous goods transport, the environment and occupational hygiene.

Microencapsulation technology is an ideal packaging system for the temporary inerting of critical working materials. Microencapsulation is understood to mean the encapsulation of finely dispersed liquid and / or solid phases by coating them with film-forming polymers which, after emulsification and coacervation or surface polymerisation, are deposited on the material to be encased. The resulting microcapsules have protective covers and can be dried to a powder. In this way, a number of substances can be converted into a "dry mass". The microcapsule content can then be released again if necessary by thermal, mechanical, chemical or enzymatic action, provided that there are still ingredients present. Practical experience, in particular from technical fields of application, shows that the microcapsule wall materials known to date are diffusion-tight and therefore sufficiently stable for only a few specific capsule ingredients. This is also one of the reasons why that they use microencapsulation technologies only in a few product segments, such as for

a) Color carrier in the coating of carbonless papers

b) pharmaceutical powder with perishable drugs, for depot preparations with or without release properties or vitamins

c) fertilizers, insecticides, herbicides, pesticides and the like, and

d) for thread locking agents

enforce. While no diffusion-tight microcapsule walls are required for product segments a) to c), this is a basic requirement for thread locking agents.

In order to achieve diffusion tightness for storage periods of up to 3 months, the microcapsule walls had to be additionally equipped with secondary or tertiary walls in separate, expensive and time-consuming process steps. Such measures have often led to unsatisfactory results.

The causes that lead to leaky protective cover walls with regard to the ingredients are often complex in nature. They do not depend solely on the number of wall layers, their strengths and properties. The essential cause parameters known to date include

the hardening of the protective walls made of hydrocolloids with aldehydes, which leads to contractions

- drying, which contributes to the additional shrinkage of the protective wall

Requellability of the hardened and unhardened protective wall in water and in polar, possibly water-containing,

REPLACEMENT BLAπ (RULE 26) organic solvents

Build up material inclusions in the protective cover wall, the so-called interlocking bridges, especially in liquid media

poor bond with 2 and multi-layer protective cover walls with each other.

For example, a number of microencapsulated products have been described for use in the technical field in patent literature. due to a lack of diffusion density and thus a lack of storage stability, they cannot find their way into industrial practice. For example, DE-OS 2027737 describes a curable multicomponent adhesive or casting compound system in which mixtures which are practically manageable can be produced by means of complex cross-combinations of unsaturated polyester resins and poly-epoxy resins and their curing agents using microencapsulation technology. At least 4 reaction partners are necessary so that the protective cover walls are characterized by an inhomogeneous leak. As a result of the microcapsule walls being too strong, a high capsule destruction rate is not ensured under application conditions. Thus, this system could not prevail in commercial practice.

In DE-OS 17 69 353 fastening and sealing means are described, which are used for the pre-coating of threaded part pairs. This is an epoxy resin adhesive system in which the reaction partner "epoxy resin" is microencapsulated in infusible aminoplast polymerisation sleeves in a non-volatile curing agent. These agents are processed from solvents that are not environment-friendly and hygienic, e.g. Chlorinated hydrocarbons and / or aro aten. In these solvents, the protective cover walls have only a limited storage stability of max. 3 months because they are not diffusion-tight and partially not resistant to the solvents. For this reason, this system has only partially been able to establish itself in practice.

SPARE BLADE (RULE 26) A large number of polymeric substances are proposed for the production of protective cover walls, the hydrocolloids taking a special position in addition to synthetic polymers. The type of capsule wall material used is largely determined by microencapsulation technology. This encapsulation technique can be in

Solvent systems and aqueous systems

divide. While microencapsulation in organic solvents has continuously lost importance due to occupational safety (possibly fire and environmental hazards), microencapsulation in aqueous media has remained as a universal technology, provided that it is possible to work without dispersants.

In the microencapsulation in the aqueous phase, hydrocolloids and / or water-soluble synthetic polymers are required for the production of protective shell walls. These wall materials include: gelatin, gum arabic, cellulose derivatives, polysaccharides, urea and / or melamine resins, polyurethane systems and the like.

In all of these aqueous microencapsulation systems, it is crucial that the substances to be encapsulated are water-insoluble but dispersible in water without damage. Furthermore, the substances to be encapsulated must be inert to the wall material medium.

The following main process steps are necessary to produce microencapsulated substances (shown simply):

Production of a stable dispersion of the substance to be encapsulated in water

Production of a colloidal solution of the selected wall material

SPARE BLADE (RULE 26) Bringing together the dispersion and the solution and then triggering solvation and coacervation so that the colloidal wall material solution can wrap around the dispersed droplets of the substance to be encapsulated as a solvate shell.

After the microcapsules have been formed, they are separated from the aqueous medium and then washed, shrunk and, if appropriate, hardened and dried with suitable hardening agents. Aldehydes, in particular glutaraldehydes, are preferably used as curing agents for hydrocolloids.

More details about microencapsulation technology can include U.S. 4,978,483; 2,712,507 and GB-A 751,600; 872 438; 927 157 and 949 910 as well as "Asaji Kondo" / J. Wade von Valkenburg, "Microcapsule Processing and Technology", Marcel Dekker Inc., New York - Basel, 1979.

Despite above-average efforts, experts failed to achieve a decisive breakthrough in the construction of storage-stable and waterproof protective cover walls with various microencapsulation technologies and conventional wall materials, especially with liquid reaction systems. It was only through the additional equipping with the above-mentioned secondary or tertiary walls that it was partially possible to achieve such a goal. As a result, new critical parameters arose when the microcapsule walls were destroyed, owing to the increased protective shell wall thicknesses. It was found that the protective cover walls cannot be broken and destroyed under the conditions of use because the pressures, torsional and shear forces required to destroy the capsules were too high. It was only through the use of protective explosive devices, as described in DE-B-25 363 319 and 27 10 548, that there were partial practical solutions.

The disadvantages described above and a number of other critical parameters are only some of the reasons for the relative

SPARE BLADE (RULE 26) Insignificance of microencapsulation technologies for packaging sensitive products and reaction systems and their use in various fields of application in the fields of technology, pharmacy and food. However, the lack of technical concepts and innovations as well as the lack of economy were and still are obstacles when opening up new areas of application for microencapsulated substances.

The object and aim of the present invention is to provide a shell material which is chemically and physically inert to the inner phase (capsule contents) and the outer phase, diffusion-tight, storage-stable, water- and / or solvent-resistant.

It has now been found that the use of hydrocolloids which are curable by polymerization and which are mono- or polysubstituted by ethylenically unsaturated radicals leads to a coating material with superior, advantageous properties.

The invention thus relates to the use of a polymer material based on one or more modified hydrocoloids with a content of> 0.1% by mass (m%) of polymerizable or crosslinkable groups of the general formula

R ¹

CH ₂ = C - X - (R ² ) _n in the

for - CO -, - COO -, - OCO -, - CONH - - CH -, - CH ₂ -, - O - or - NR ³ - i.

stands;

R ^{1 represents} a hydrogen atom, a hydroxyl, nitrile, halogen or C * -C ₄ alkyl radical;

SPARE BLADE (RULE 26) R ² represents a saturated or unsaturated, at least divalent hydrocarbon radical, which if appropriate has one or more substituents selected from hydroxy, A ino-, C _j -C ₈ - alkyl, Cj-Cg alkoxy and / or hydroxy-C, -C ₈ -alkyl group and which optionally has one or more hetero groups which are selected from - CO -,

- OCOO -, - COO -, - OCO -, - 0 -, - S -,

- NR ⁴ -, - NHCO -, - CONH -, - NHCONH -;

R ³ and R ⁴ , which may be the same or different, represent a hydrogen atom, a hydroxyl group or a C _j -C ₄ alkyl radical and

n represents 0 or 1; these groups are connected by a link to the backbone of the hydrocolloid, as a covering material for critical working materials.

Critical working substances in the sense of the present invention are the beginning or. understand below defined substances as well as pharmaceutical and cosmetic products. The polymer material is particularly useful as a diffusion-tight covering material for protecting the coated products from external influences and reactive components and for protecting the environment from the properties of the coated products.

The use of the polymer material as a microcapsule wall material, as a coating material for drug forms or as a material for macrocapsules, in particular drug capsules, is particularly preferred.

When used as a microcapsule wall material, in particular dangerous, toxic, flammable, autoxidable, volatile, thermosensitive and / or reactive agents and reaction systems can be packaged. In particular, polymerizable compounds; reactive compounds that harden according to the principle of polyaddition; hardening compounds; (reactive

SPARE BLADE (RULE 26) ve) adhesives or sealants; Dowel compounds; sensory, fragrant and / or smelling substances; coloring substances, dyes or colors; Paints; Coatings; Casting compounds, blowing agents and foaming agents; autoxidationse pf indigenous substances etc. Pack stable and diffusion-tight.

Under reaction systems within the meaning of the present invention. a. to understand:

- All 2- and multicomponent products which react with and with one another during or after mixing together and can be crosslinked via polymerization, polyaddition and polycondensation (examples of these are: reaction lacquers, reaction adhesives and reaction sealants and / or

change chemically and / or physically depending on the respective environmental conditions - even with one-component systems - such as B. by evaporation of ingredients, oxidation and the like.

Particularly in the case of reaction systems, it is of particular importance that the protective cover walls, in particular in liquid media, are diffusion-tight and that no diaphragm or membrane properties develop. This critical parameter of diffusion tightness is particularly important when, for example, even very small amounts of an ingredient can migrate through the protective cover wall due to migration and / or diffusion and can trigger unwanted reactions prematurely. As a result, a wide variety of undesirable moments of danger are preprogrammed and the product can no longer be used for its actual purpose.

The term "diffusion-tight" includes u. a. the following.

No exchange of ingredients from the inner (microcapsule content) to the outer phase and vice versa

Diffusion and / or migration during storage in liquid media, dry substances and / or in a given environment.

SPARE BLADE (RULE 26) A test method suitable for industrial practice has been developed for assessing and classifying the so-called diffusion tightness of a wall material according to the present invention. Here, the microencapsulated substances are stored for a predetermined time unit "X" in a suitable, inert test medium, moved therein and / or heated if necessary. The test medium is preferably an inert organic solvent and / or water.

Those wall materials that diffuse or migrate into the inert outer test medium phase during the predetermined time unit “X” vorgegebenen 5.0, preferably <3.0, in particular <1.0 m% of one or more microcapsule ingredients are classified as diffusion-tight leave and give away.

The diffused and / or migrated ingredients are then qualitatively and quantitatively analytical, e.g. determined by gas chromatography.

The envelope material used according to the invention is based on functionalized hydrocolloids. The starting materials for their manufacture include known and conventional hydrocolloids or their basic raw materials. The chemical modification of the starting materials takes place by introducing side chains into the main molecular chains via reactive and / or functional groups without changing or damaging the colloid chemical and water-soluble properties.

By preserving the colloid chemical and possibly the water-soluble properties after the chemical modification of the hydrocolloids, the shell materials can be prepared by conventional methods, e.g. using conventional microcapsule techniques, use and process. However, the hydrocolloids modified according to the invention have additional product parameters which already have a positive effect before, during and / or after coacervation, during curing and / or crosslinking. They therefore make an essential contribution to the construction and formation of inert, optionally waterproof and diffusion-tight envelope materials.

SPARE BLADE (RULE 26) The shell materials according to the invention are reactive, biodegradable hydrocolloids or backbone polymers. They result from an at least partial derivatization of the functional groups of the starting materials mentioned, for example hydroxyl, amino, imino, thiol and / or carboxyl groups, with a polymerizable radical of the general formula

R ¹

in which X, R ¹ , R ² and n have the meaning given above,

in a non-radical reaction. The radicals introduced into the main molecular chains of the hydrocolloids according to the present invention are ethylenically unsaturated radicals. These can be connected to the hydrocolloids directly or via the radical R ² , for example a divalent, optionally substituted, aliphatic carbon, hydrogen or polyol radical. The link between this residue and the polymer main chain accordingly results from the reaction of the functional groups of the hydrocolloid with the corresponding reactive groups of the polymerizable residue mentioned. In particular, the link is the same group as the hetero groups of the radical R ² .

The hydrocoloid derivatives used according to the invention as envelope materials are water-soluble polymer materials which are functionalized by means of ethylenically unsaturated compounds according to the general formula above. The radical R ² is at least one

R ¹ CH ₂ = C - X group, in which R ¹ and X can have the above meaning and where several

SPARE BLADE (RULE 26) R ¹

I CH ₂ = C - X radicals within the polymer material, the radicals R ¹ or X can each be the same or different. Any hetero groups of the radical R ^{2 which are present} can be arranged as bridging members to X or A both within the radical, in particular in the case of aliphatic radicals R ² and / or at one or both ends of the radical R ² .

In a particularly preferred embodiment, R ^{2 is} an at least divalent optionally substituted glycol or polyol radical with 2-6 C atoms, the divalent radical of an oxy- or hydroxycarboxylic acid with 2-18 C atoms or the divalent radical one Carboxylic acid C ₂ -C ₆ glycol or C ₆ -C ₈₀ polyalkylene glycol ester. In particular, the radical R ^{2 is} a C _j -C ₄ alkylene group which is optionally substituted by hydroxyl, amino and / or lower alkyl groups. R ² can also have acyloxy, carbonyl, carbonyldioxy, carbamoyl, hydroximino, imino, ureylene and / or nitrilo bridge members (hetero groups). The ureylene bridge member is very particularly preferred.

The radical R ² is preferably connected to the hydrocolloid A via ether, ester and / or imino groups (Y • = -0-, -0C0-, -C00- or -NR ⁴ ). It is particularly preferred: R ¹ = H or CH ₃ ; X = -COO-, -O- or -CH ₂ -; R ² - aliphatic hydrocarbon radical, in particular a C ₂ -C ₁₀ alkylene radical or the radical (CH ₂ CH ₂ 0) _m with m = 1-5. The functionalization of the hydrocolloids A with one or more reactive radicals takes place in particular via their Hydroxy1, amino, imino, thiol and / or carboxyl groups. The content of functional residues in the hydrocolloid A is ≥ 0.1 m%. The particularly preferred contents are in the range from 1 to 50 m%, in particular 5 to 30 m%.

The starting material for the water-soluble, biodegradable hydrocolloids or backbone polymers can come from the following polymer families:

SPARE BLADE (RULE 26) - Proteins: polypeptides, especially those of collagenous origin such as. e.g. B. Gelatin, animal glues, whey proteins, casein, vegetable proteins, especially soy proteins and the like. and their hydrolysates

- Polysaccharides: cellulose and its derivatives, such as methyl cellulose, ethyl cellulose, hydroxy ethyl cellulose, carboxy ethyl cellulose, etc. , Starch and starch derivatives, glycogen, alginic acid and derivatives including salts, agar agar, heteropolysaccharides, heteroglycans, hemicelluloses and their derivatives, chitin, gum arabic and the like.

The derivatization can take place by non-radical reaction or by grafting reactions on the backbone polymers.

According to the invention, however, preference is given to the functionalized backbone polymers or hydrocolloids in which the reactive groups have been introduced into the main molecular chains via a non-radical reaction. They contribute significantly to a homogeneous spectrum of properties, as has surprisingly been found. These functionalized products are produced by methods which are known to the person skilled in the art for the introduction of such side chains. For example, the functional groups of the hydrocolloid can be reacted with a reactive derivative of the side chain residue or vice versa. The reaction of amino groups with corresponding alkyl and acyl halides, acid anhydrides or epoxides, the reaction of hydroxyl groups or thiol groups with corresponding alkyl and acyl halides, acid anhydrides, carboxylic acids or epoxides and the reaction of carboxyl groups with alcohols or epoxides, etc. should be mentioned here The production of such polymer materials is described, for example, in DE-A-42 10 334, to which reference is hereby made. Accordingly

SPARE BLADE (RULE 26) suitable for functionalizing a large number of unsaturated compounds, in particular those containing acrylic, methacrylic and allyl groups, according to the above formula. Particularly preferred are such reactive groups which, inter alia, on Acrylsäureglycidyle- ster, glycidyl methacrylate, Acryloxypropion- acid glycidyl ester, Methacryloxypropionsäureglycidylester, Maleinsäuremonomethylacryloyloxiethylester, Diurethanmethacry- acrylate and allyl glycidyl carbonate, and (meth) acryla id are introduced into the hydrocolloid A.

The polymerization required for curing can be carried out by homopolymerization of a hydrocolloid derivative containing the unsaturated radicals, but also by copolymerization of a mixture of such derivatives.

The polymerization or copolymerization required for curing is carried out by adding or mixing in, by spraying, coating and / or in a bath with the reaction initiators required for systems of this type. These include

inorganic per compounds such as e.g. Hydrogen peroxide, alkali and alkaline earth peroxides, persulfates, percarbonates

organic peroxides such as Methyl ethyl ketone peroxides, cyclohexane peroxides, dibenzoyl peroxides, p-chlorobenzoyl peroxide, acetylacetone peroxide, cumene hydroperoxide and other initiators that trigger polymerizations.

But also high-energy rays such as UV rays in the presence of a photoinitiator or electron beams can start the polymerization and copolymerization.

Furthermore, the polymerization and copolymerization can be accelerated by adding an accelerator after the addition of one or more reaction initiators, so that they can also be carried out at lower temperatures. For this purpose, accelerators are among others. based on heavy metal salts such as Cobalt acetylacetonate, vanadium naphthenate, tertiary amines such as e.g.

SPARE BLADE (RULE 26) Diethylaniline, diethyl-p-toluidine, triethanolamine are suitable.

The functionalized hydrocolloids according to the invention can be modified by further additives. Suitable additives include Plasticizers, dyes, pigments, inorganic and / or organic fillers and fibers. Stabilizers and / or inhibitors can also be added.

The use of mixtures of the hydrocolloids according to the invention with non-functionalized hydrocolloids can be particularly preferred if the coating materials have specific functions such as e.g. partial swellability in water have to be met, as has surprisingly been found.

In a number of applications, the shell materials, in particular the microcapsule walls, must be more inert against specific chemical and / or environmental influences than can be achieved with the polymer crosslinking according to the invention. In order to achieve this goal - depending on the respective media - the remaining functional groups present in the hydrocolloid can be partially or completely reacted or rendered inert with other compounds which serve to harden or crosslink. These include Aldehydes, e.g. Formaldehyde, acetaldehyde, glutaraldehyde, compounds containing aldehyde groups, such as urea, melamine and / or phenolaldehyde condensates, isocyanates and their prepolymers, such as tri (p-isocyanato-phenyl ester), diphenylmethane-4,4'-dii εocyanate, hexamethylene diisocyanate.

Furthermore, shrinking of the enveloping material, in particular the microcapsule walls, may be necessary in individual cases. This shrinking takes place after the formation of the protective cover walls by means of known, conventional methods, such as e.g. with sodium sulfate solutions.

All process techniques in which water-soluble hydrocolloids can be used are suitable for forming microcapsules. These include

SPARE BLADE (RULE 26) Physical process: stationary extrusion, centrifugal

Extrusion, rotating plate process, spray drying, air suspension process, dipping, spraying, dragging and the like.

Chemical processes: interfacial polymerization, coacervation, in-situ polymerization and the like

The microcapsules are produced as stated at the beginning. The hardening or crosslinking of the protective cover walls can be carried out continuously and discontinuously. In the case of free radical curing or crosslinking, the microcapsules are placed in a bath in which the compounds used for curing or crosslinking are dissolved and / or dispersed. Water and / or organic solvents are suitable as solvents, water being preferred according to the invention. The concentrations of these hardener solutions depend on the desired hardening time and temperature. To accelerate the free radical curing or crosslinking, accelerating compounds can be added to the hardener solution or can be carried out in a separate accelerator bath after the curing. The protective cover walls can also be hardened or crosslinked by spraying on the hardener and / or accelerator solutions.

The microcapsule walls can also be hardened or crosslinked using high-energy rays. When curing or crosslinking with UV rays, the hydrocolloids according to the invention are one or more photosensitive compounds, such as Benzoin and derivatives, benzil dimethyl ketals, 1-hydroxycyclohexyl phenyl ketones, benzophenones, 2,4,6-trimethylbenzoyldiphenyl phosphine oxides, alone or in combination with amine group-containing co-initiators, such as e.g. 2- (Dimethylamino) ethylbenzoate. No initiator additives are required for hardening or crosslinking with electron beams (ES). Radiation cans and

The duration of exposure depends on the one hand on the contents of reactive groups in the hydrocolloids according to the invention and on the other hand on the microcapsule wall thicknesses and the contents.

ERSArZBLATT (REGEL26) Substances dependent on the microcapsules. The exposure times are generally between 1 and 300 seconds for UV crosslinking with UV lamps with a power of 80 to 100 W / cm and for ES crosslinking between 5 and 70 kGy.

In order to achieve storage-stable, water-resistant and / or diffusion-tight microcapsule walls, dual curing or crosslinking may be indicated. Dual hardening or crosslinking according to the present invention means that other functional groups present in the hydrocolloids A, which can react according to other reaction mechanisms, during and / or separately from the free radical hardening or crosslinking with the suitable hardening or Networking connections are implemented. An example of this is the peroxidic curing or crosslinking and the reaction of -NH and / or OH groups of the hydrocolloids A with isocyanate groups in one or two separate steps.

Due to the dual hardening or networking, among other things Build up additional hydrophobic bridge members in the protective shell wall material, whereby the water resistance can be increased essentially and the water swellability can be considerably reduced, as was surprisingly found without reducing the elasticity of the toughness.

The microcapsule wall materials according to the invention can be used to solve and simplify further tasks in enveloping and protecting gases and particles from liquids, pastes and dry substances. Depending on the respective physical and / or chemical microencapsulation techniques, especially for industrial production, reproducible parameters can be developed and set because the hydrocolloids according to the invention have more homogeneous properties compared to the conventional microcapsule wall materials.

SPARE BLADE (RULE 26) For example, the solutions of the microcapsule wall materials according to the invention can be added with the compounds used for curing or crosslinking. Particularly suitable for this are those per compounds and / or peroxides which only act as initiators at elevated temperatures and thus have sufficient pot lives. This has the advantage that the hardening or crosslinking can be initiated immediately after the protective shell walls have been formed. Hardening or crosslinking can be accelerated by spraying a solution of reaction accelerators onto the protective cover walls and / or introducing the microcapsules into an accelerator bath.

The protective cover walls can also be hardened or crosslinked in hardening and / or accelerating baths, if appropriate tempered.

In chemical microencapsulation techniques, in particular in the coacervation process, the microcapsule wall materials according to the invention offer further advantages, as has surprisingly been found. When a solution of the hydrocolloids according to the invention is introduced into liquid media with dispersed particles or droplets to be coated (stable dispersion)

draw the wall materials onto the dispersed particles or droplets faster and form more homogeneous protective shell walls by coacervation

- The resulting microcapsule spectra have after

Gaussian distribution curve has smaller coefficients than the microcapsules produced with conventional hydrocolloids.

Furthermore, when using the hydrocoloids according to the invention, the proportion of free coacervates is surprisingly low, which among other things reduce the washing times considerably.

SPARE BLADE (RULE 26) Another essential feature is the possibility of a homogeneous hardening or crosslinking and the formation of bridge members (crosslinking) in order to arrive at a more stable capsule wall matrix. By hardening or crosslinking, the hydrocolloids according to the invention become their sol / gel

Transfor ation properties taken, which among other things has a beneficial effect on dehydration and drying.

The points mentioned, i.e. The rapid formation of the protective shells with the hydrocolloids according to the invention, the uniform wall thicknesses of the microcapsules obtained and the formation of narrow microcapsule spectra with round and / or ellipsoidal microcapsule shapes are particular advantages of the present invention.

The present invention solves further essential tasks in the dehydration and drying of protective cover walls. While a number of very critical, changing parameters are present in the dehydration and drying of protective casings made from conventional hydrocolloids, which can optionally be hardened with aldehydes according to the prior art, these do not occur when using the wall materials according to the invention. In the case of conventional protective wall materials, these critical parameters include based on the fact that it

have different degrees of hardening as a result of inhomogeneous wall thicknesses, which contribute to the development of internal stresses and thus to the formation of cracks in the protective sheaths

still as gels, low melting points due to the (partially) existing sol / gel transformation properties

and

SPARE BLADE (RULE 26) have too long dehydration and drying times - often several days - at relatively low temperatures, even when using modern drying techniques.

If, on the other hand, the protective cover walls consist of the hydrocolloids according to the present invention, the above and other disadvantages can not only be eliminated, but they also offer further advantages as homogeneously hardened or crosslinked gels, as has surprisingly been found. One of these advantages according to the invention is that the dehydration and drying of the hardened or crosslinked protective shell gels can be accomplished in a fraction of the time as with conventional hydrocolloids with increasing temperatures, depending on the thermosensitivity of the encapsulated ingredients. It is particularly preferred for dehydration and drying according to the present invention to use conditioned drying air which has a relative air humidity <50%, in particular <40%, and drying air temperatures between 20 ° C. and 100 ° C.

Under such conditions, the protective cover gels according to the invention dehydrate and dry

Lower contraction and less stress - preferably keep their more stable round and / or elipsoid For any reactive groups that may be present can react.

Furthermore, the hardened or cross-linked protective gel gels according to the present invention only require a fraction of drying aids such as e.g. expensive pyrogenic silica compared to conventional processes.

The polymer material is also suitable for coating drug forms, in particular coated tablets, capsules and tablets. The polymer material can be chosen so that an enteric coating or an enteric coating results.

SPARE BLADE (RULE 26) The pharmaceutical forms are coated in the customary manner, for example by spraying.

Furthermore, the polymer material can also be used in the form of macrocapsules for coating the above-mentioned products. Pharmaceutical capsules are particularly worth mentioning here. A gelatin-based polymer material is then preferably used. Both full capsules and push-fit capsules can be produced. The capsules are produced in the usual way.

Through the use of the hydrocolloids according to the present invention as microcapsule wall materials, modern microencapsulation technology is not only given new impulses for the more economical production of protective sleeves with functionally reliable membrane properties and. improved storage stability, but also created the conditions to use them industrially and commercially. This is because storage-stable, waterproof and, if necessary, diffusion-tight packaging systems such as the microcapsules create the prerequisites for the temporary inerting of dangerous, toxic, flammable, autoxidable, volatile, i.e. evaporating or sublimating, thermally sensitive and / or reactive working materials and systems. The simultaneously simplified process technology also ensures a high level of economy.

The invention is explained in more detail by the following examples, but without being restricted thereto.

The wall materials used had the following technical characteristics: Wall material A = derivatized gelatin (according to the invention) Gelatin strength according to Bloom: 272 g viscosity according to Bloom / 50 ° C 50 mPa.s

Glycidyl methacrylate content: 1.7 mmol / g

Wall material B = unmodified gelatin (comparison) gelatin strength according to Bloom: 272 g viscosity according to Bloom / 50 ° C: 50 mPa.s

Example 1

In a double-walled mixing container with a net capacity of 100 liters and equipped with a continuously variable agitator

40.0 liters of water and 2.0 kg of wall material A

submitted. Wall material A was allowed to swell in cold water and the mixture was then heated to about 45 ° C. without stirring. This temperature of 45 ° C was maintained. After the wall material A had dissolved, 0.5 kg of sodium polyphosphate and 0.3 kg of sodium acetate were added with the agitator running and mixed in homogeneously.

15 kg of benzoyl peroxide paste, 50% in dibutyl phthalate, were dispersed well into this prepared wall material solution and the remaining amount of water of 10 liters was added. With stirring, the pH of the mixture was lowered to the coacervation point (approx. PH 4.2) using 10% acetic acid. The mixture was then slowly cooled to a temperature of 10 ° C.

The pH was adjusted to about 5 by adding a 5% sodium hydroxide solution and a 50% glutaraldehyde solution for pre-curing the finished wall was added. This pre-curing with the glutaraldehyde solution took about 24 hours. For further hardening or crosslinking of the functional parts About 0.250 kg of sodium peroxodisulfate (Na ₂ S ₂ 0 ₈ ) were added to the batch of methacrylic groups of wall material A and homogeneously dissolved and distributed by stirring. To accelerate this reaction, 0.250 liters of 50% triethanolamine were added. After a stirring time of about 8 hours, this hardening was complete.

The microcapsules formed were then allowed to sediment and washed 3 times with fresh water.

After the washing process, a drying aid, e.g. pyrogenic silica, mixed in and the microcapsule suspension was filtered.

The wet microcapsule cake obtained (60-70% water content) was then dried in a fluidized bed dryer with increasing drying air temperature from 18 ° C to 40 ° C and a relative humidity <40%. The drying time was 18 hours. The microcapsules obtained were in the form of individual capsules and were free-flowing.

Example 2

Example 1 was repeated in such a way that a 15 kg bisphenol A dimethacrylate / triethylolpropane trimethacrylate mixture (1: 1) was encapsulated instead of the benzoyl peroxide paste. The other process conditions corresponded to Example 1. The drying time was 17 hours.

Example 3 (comparison)

Example 1 was repeated in such a way that instead of

Wall material A the wall material B was used.

Example 4 (comparison)

Example 2 was repeated in such a way that instead of

Wall material A the wall material B was used. Example 5

This example differs from the above in that the hardening or crosslinking of the methacrylic groups in the wall material A is initiated with the onset of coacervation.

Example 2 was repeated in such a way that 0.250 kg of sodium peroxodisulfate were dissolved in the residual water amount of 10 liters before the start of coacervation and then added to the batch. When the coacervation began, the hardening or crosslinking of the wall material A was also initiated. Since free radical curing or crosslinking takes place more slowly in the acidic area, no stresses build up in the wall material and it is hardened more homogeneously and more stably. Glutaraldehyde curing was not carried out. Otherwise, the procedure was as in Example 1.

The results are summarized in Table 1.

Capsule drying residual moisture diffusion Note: large (40% relative humidity) d.Micro capsule - in% after days

Deipiel No. μm ° C hour wall% 10 90

1 (according to the invention) 50-120 18-40 18 '- 2.0 0.01 0.00 individual capsule'

2 (according to the invention) ^{80-200 18-60} 17 ^{* ■} 2.0 0.02 0.03 individual capsule

3 (comparison) 50 - 120 18 - 40 96 - 2.0 2.1> 5.0 clouster nests

4 (comparison) 80 - 200 18 - 60 48 - ^" 2.0 3.4> 5.0 Clouster nests

5 (according to the invention) ^{40-100 20-00} 12 ^{* ■} 2.0 0.01 0.01 individual capsule

1) The diffusion tightness of the microcapsule walls was tested in toluene. 90 parts by weight of toluene and 10 parts by weight of microcapsules were weighed into a sealed glass bottle and a suspension was prepared therewith. The suspension was shaken continuously and after 10 and 90 days a sample was taken from the liquid toluene phase and gas-roasted fish examined for the content of ingredients.

2) Oβi peroxidic ingredients have the wall material according to the invention "self-healing" effects by post-curing.

Example 6

For the production of tough elastic microcapsule walls with low oxygen permeability, a gelatin modified with glycerinallyl ether was used with the following characteristics:

Gelatin strength according to Bloom: 255 g

Bloom viscosity / 60 ° C: 25 mPa.s

Glyceryl allyl content: 1.9 mmol / g

An oxidation-sensitive coffee aroma was microencapsulated with this wall material using the method described in Example 1. Glutaraldehyde precuring and free-radical crosslinking with sodium peroxodisulfate were dispensed with. At the end of the drying process, the wall material was hardened with electron beams and a radiation dose of 20 kGy. - In parallel, films with a wall thickness of 15 μm were produced in an analogous manner on a glass plate from the wall material in order to be able to determine the oxygen permeability of the wall material. The oxygen permeation (ASTM) was 25 ml / d / m ² / bar at 25 ° C / 0% relative air humidity. The gelatin wall had tough elastic properties. The microencapsulated coffee aroma was checked again after 3 months of storage in daylight. The coffee aroma showed no changes in an organoleptic test that could be attributed to auto-oxidation.

Example 7

For the microencapsulation of an epoxy resin (viscosity 750 mPa.s, epoxy value 0.54), an acrylamide-modified gelatin with the following characteristics was used:

Gelatin strength according to Bloom: 245 g Viscosity according to Bloom / 50 ° C: 45 mPa.s Acrylic group content: 1.68 mmol / g

The microencapsulation was carried out according to Example 1.

The microcapsule walls were absolutely tight after 6 months of toluene storage. In addition, a "self-healing" effect on mechanically damaged microcapsule walls was also possible to be watched. This is probably due to the -NH groups from the acrylamide, which have reacted with the epoxy groups of the epoxy resin.

Example 8

A thin-boiling corn starch with a content of 1.4 mmol / g of glycidyl methacrylate was selected for coating tablets (coated tablets). The shell material had the following composition:

5.00 parts by weight of the above gelatin

12.00 parts by weight of color pigment "red" on the basis of '

Iron oxides 83.00 parts by weight of distilled water

The wall material was suspended in the cold distilled water and the suspension was then heated in a beaker and briefly boiled. The color pigment was dispersed into the starch solution obtained on cooling.

The coating material solution was then processed using an airless, multi-component spray gun. The hardener solution consisting of a 10% potassium peroxodisulfate solution in water was simultaneously fed to the multi-component nozzle. The mixing ratio was 10: 1 (starch solution to hardener). Spraying was carried out at 60 ° C.

1000 g of tablets were placed in a rotating drum and these were sprayed with the coating material via the airless spray gun.

The spraying process was ended after 30 minutes and the coated tablets were subsequently dried with a warm air stream (80 ° C.), with the acrylic-modified starch being cured at the same time.

The tablets showed a homogeneous, red coating layer, which was also stable against mechanical loads.

Claims

Patent claims

1. Use of a polymer material based on one or more modified hydrocolloids with a content of> 0.1 mass% (m%) of polymerizable or crosslinkable groups of the general formula

R ¹ CH ₂ = C - X - (R ² ) _n - in the

for - CO -, - COO -, - OCO -, - CONH -

- -, - CH ₂ -, - O - or - NR ³ -

stands;

R ^{1 represents} a hydrogen atom, a hydroxyl, nitrile, halogen, or C - C ₄ alkyl radical;

R ² represents a saturated or unsaturated, at least divalent hydrocarbon radical, which if appropriate has one or more substituents selected from hydroxy, amino, C _j - C ₈ alkyl, C _j -CG-alkoxy and / or hydroxy-C _j -C ₈ alkyl group and optionally having one or more rogruppen Hete¬, which are selected from - CO -, - OCOO -, - COO -, - OCO -, - 0 -, - S -, - NR ⁴ -, - NHCO -, - CONH -, - NHCONH -;

R ³ and R ⁴ , which may be the same or different, stand for a hydrogen atom, a hydroxyl group or a C.-C ₄ alkyl radical and

n represents 0 or 1; these groups being connected by a link to the backbone of the hydrocolloid, as a covering material for critical working materials.

2. Use according to claim 1, wherein R ¹ in formula I represents a hydrogen atom or a C ₁ -C ₄ alkyl group.

3. Use according to claim 1 or 2, wherein X in the formula I is - COO -, - O - or CH ₂ -.

4. Use according to any one of claims 1 to 3, wherein R ² in the formula I for an optionally substituted by a hydroxyl group ethylene, propylene or butylene radical or for a radical of the formula (-OCH ₂ CH ₂ -) _m stands, where m stands for 1 to 5.

5. Use according to any one of claims 1 to 3, wherein the polymerizable or crosslinkable groups are derived from glycidyl acrylate or glycidyl methacrylate.

6. Use according to one of the preceding claims, wherein the link to the backbone of the hydrocolloid is a group which is selected from - CO -, - OCOO -, - COO -, - OCO -, - 0 -, - S -, - NR ⁴ -, - NHCO -, - CONH - or - NHCONH -.

7. Use according to any one of the preceding claims, wherein the hydrocolloid is selected from a polypeptide of collagen origin, in particular gelatin, animal glue, collagen; Caseins, whey proteins; Vegetable proteins, in particular soy proteins, or a hydrolyzate thereof and a polysaccharide, in particular cellulose or starch or a derivative thereof.

8. Use according to one of the preceding claims, wherein at least 10 crosslinkable groups per 1000 amino acids or monosaccharide units are present in the hydrocolloid.

9. Use according to one of the preceding claims, which additionally contains non-functionalized hydrocolloids.

10. Use according to one of the preceding claims, wherein 5 the polymer material is used as microcapsule wall material as w coating material for pharmaceutical forms or as capsule material.

11. Use according to claim 10 as a microcapsule wall material 10 for packaging dangerous, toxic, flammable, autoxidizable, volatile, thermosensitive and / or reactive materials and systems or of pharmaceuticals.

12. Use according to claim 11 for packaging

15 polymerisable compounds, in particular (eth) acrylic, allyl and / or vinyl group-containing curable compounds;

reactive compounds which harden according to the principle of polyaddition, in particular compounds containing epoxy and / or isocyanate groups;

hardening compounds;

25 reactive adhesives and sealants;

sensory, scented and / or smelling substances;

coloring substances and / or dyes; 30

Blowing and foaming agents; and or

c autoxidationse sensitive substances.

35 13. Storage-stable microcapsules made of a wall material as defined in one of claims 1 to 9.

14. A method of forming an envelope, characterized characterized in that one of the modified hydrocolloids defined in claims 1 to 7 is subjected to coacervation and subsequent polymerization or crosslinking, in the presence of the material to be encapsulated and, if appropriate, in the presence of customary additives, in an aqueous medium.

15. The method according to claim 14, characterized in that the microcapsules are additionally hardened.

16. The method according to claim 15, characterized in that a dual curing or crosslinking is carried out.

17. The method according to any one of claims 14 to 16, characterized in that a post-curing and drying of the microcapsule walls is carried out by dehydration under conditioned air with a relative air humidity <50% and temperatures between 20 ° C and 100 ° C.